In order to prevent a connected portion, that is, a joint portion, of general pipes from being displaced and to prevent generation of gaps at the joint portion, a pipe clamp is used. As shown in FIG. 1, the pipe clamp includes a pair of bodies 1, a link 2 for rotatably connecting the pair of bodies 1, a fastening bar 3 for fastening the pipe clamp, and a screw 4 for moving the fastening bar 3.
The body 1 is provided with a fastening protrusion 1a into which the fastening bar 3 is fitted for coupling thereto. The fastening protrusion 1a is provided at a portion thereof that has an anti-rotation protrusion 1b for preventing the rotation of the fastening bar 3, which is coupled to the fastening protrusion 1a. 
However, such conventional pipe clamps have the following problems.
1. When the joint portion of pipes is relatively small compared to the pipe clamp, there is a problem whereby the joint portion is not firmly clamped by the pipe clamp.
2. When the joint portion of pipes is relatively large compared to a pipe clamp, the fastening bar is not firmly fastened to the fastening protrusion. Accordingly, there is a problem whereby the pipe clamp becomes separated from the joint portion of the pipes.
3. Although the fastening bar coupled to the fastening protrusion is prevented from being rotated by the anti-rotation protrusion, there is a problem whereby the fastening bar is rotated and thus released when an external impact or the like is applied to the anti-rotation protrusion.